Cellulose whiskers are increasingly being used as a reinforcing phase in polymer systems and their use is a growing area of importance in bionanocomposite research. Although the reinforcing effect of cellulose whiskers has been studied in various polymers, the impact of crosslinking cellulose whiskers has not been explored so far. This work deals with the development of novel cellulose nanocomposites, wherein the cellulose nanowhiskers are crosslinked with poly(methyl vinyl ether-co-maleic acid) and poly(ethylene glycol). The morphology of the nanocomposite was studied using atomic force microscopy (AFM), which revealed a network structure embedded in a continuous phase. The water sorption studies demonstrated that the crosslinked nanocomposites are capable of absorbing up to ~ 900% water and have potential to be used as hydrogels.

Cellulose nanocrystals (CNC) were extracted from a cellulose residue using two different acid hydrolysis procedures. CNC extracted with sulfuric acid (CNCS) showed higher surface charge (339 μmol/g) compared with crystals extracted with hydrochloric acid (CNCHCl). Spin-coated films with two different configurations were prepared; the first with alternate layers of poly(allylamine hydrochloride) (PAHCl) and CNC, and the second with a single layer of PAHCl coated with multilayers of CNC. Film characteristics such as roughness, thickness, contact angle, orientation, gas permeability and gas selectivity were studied. Optical microscopy showed more homogeneous films of CNCS compared to CNCHCl. The surface charge of the crystals impacted the films’ hydrophobicity, being highest for 25 alternate layers of PAHCl and CNCHCl. The gas permeability coefficient was different for each film, depending primarily on the surface charge of the crystals and secondly on the film configuration. The films made with CNCHCl displayed gas barriers with nitrogen and oxygen, and gas selectivity with some gas combinations. CNCS films did not show gas selectivity. These results indicate that CNC with low surface charge can be further developed for gas separation and barrier applications.

Fully biobased composite membranes for water purification were fabricated with cellulose nanocrystals (CNCs) as functional entities in chitosan matrix via freeze-drying process followed by compacting. The chitosan (10 wt%) bound the CNCs in a stable and nanoporous membrane structure with thickness of 250-270 μm, which was further stabilized by cross-linking with gluteraldehyde vapors. Scanning electron microscopy (SEM) studies revealed well-individualized CNCs embedded in a matrix of chitosan. Brunauer, Emmett and Teller (BET) measurements showed that the membranes were nanoporous with pores in the range of 13-10 nm. In spite of the low water flux (64 L m-2 h-1), the membranes successfully removed 98%, 84% and 70% respectively of positively charged dyes like Victoria Blue 2B, Methyl Violet 2B and Rhodamine 6G, after a contact time of 24 h. The removal of dyes was expected to be driven by the electrostatic attraction between negatively charged CNCs and the positively charged dyes.

In the present research work, dicationic ionic liquids, containing 1,1-Bis(3-methylimidazolium-1-yl) butylene ([C4(Mim)2]) cation with counter anions [(2HSO4)(H2SO4)0], [(2HSO4)(H2SO4)2] and [(2HSO4)(H2SO4)4] were synthesised. ILs structures were confirmed using 1H NMR spectroscopy. Thermal stability, Hammett acidity, density and viscosity of ILs were determined. Various types of lignocellulosic biomass such as rubber wood, palm oil frond, bamboo and rice husk were converted into LA. Among the synthesized ionic liquids, [C4(Mim)2][(2HSO4)(H2SO4)4] showed higher % yield of LA up to 47.52 from bamboo biomass at 100 °C for 60 min, which is the better yield at low temperature and short time compared to previous reports. Surface morphology, surface functional groups and thermal stability of bamboo before and after conversion into LA were studied using SEM, FTIR and TGA analysis, respectively. This one-pot production of levulinic acid from agro-waste will open new opportunity for the conversion of sustainable biomass resources into valuable chemicals.

Nano-sized cellulose ester derivatives having phosphoryl side groups were synthesised by phosphorylation of nanofibrilated cellulose (NFC) and nanocrystaline cellulose (NCC), using different heterogeneous (in water) and homogeneous (in molten urea) processes with phosphoric acid as phosphoryl donor. The phosphorylation mechanism, efficacy, stability, as well as its influence on the NC crystallinity and thermal properties, were evaluated using ATR-FTIR and 13C-NMR spectroscopies, potentiometric titration, capillary electrophoresis, X-ray diffraction, colorimetry, thermogravimmetry and SEM. Phosphorylation under both processes created dibasic phosphate and monobasic tautomeric phosphite groups at C6 and C3 positioned hydroxyls of cellulose, yielded 60-fold (∼1173 mmol/kg) and 2-fold (∼1038 mmol/kg) higher surface charge density for p-NFC and p-NCC, respectively, under homogenous conditions. None of the phosphorylations affected neither the NC crystallinity degree nor the structure, and noticeably preventing the derivatives from weight loss during the pyrolysis process. The p-NC showed high hydrolytic stability to water at all pH mediums. Reusing of the treatment bath was examined after the heterogeneous process.

Fibrous cellulose nanocomposites scaffolds were developed and evaluated for their potential as ligament or tendon substitute. The nanocomposites were prepared by partial dissolution of cellulose nanofiber networks using ionic liquid at 80 °C for different time intervals. Scanning electron microscopy study indicated that partial dissolution resulted in fibrous cellulose nanocomposites where the dissolved cellulose nanofibers formed the matrix phase and the undissolved or partially dissolved nanofibers formed the reinforcing phase. Mechanical properties of the composites in simulated body conditions (37 °C and 95% RH) after sterilization using gamma rays was comparable to those of natural ligaments and tendons. Stress relaxation studies showed stable performance towards cyclic loading and unloading, further confirming the possibility for using these composites as ligament/tendon substitute. In-vitro biocompatibility showed a positive response concerning adhesion/proliferation and differentiation for both human ligament and endothelial cells. Prototypes based on the cellulose composite were developed in the form of tubules to be used for further studies.

Microorganisms can spread on the surface of banknotes and cause many infectious diseases. Chitosan nanofibers (CNFs) and cellulose nanocrystals (CNCs) are nanomaterials, which can affect the antimicrobial properties. In this study, the fungal species that grew on the surfaces of collected banknotes from different places were identified. To examine the antifungal effect of the both nanomaterials on the banknotes, the stable coatings using CNFs and CNCs emulsions were prepared by roller coating. The results revealed that the most colonies in the banknotes obtained from the bakeries and butcheries were Aspergillus sp., whereas the colonies in bus terminals and the hospitals were Aspergillus niger and Penicillium, respectively. The results showed that the CNCs had no antifungal effect alone on the aforementioned species, but it could improve the antifungal effect, adhesion, and stability of CNFs on the banknote surfaces. This study suggested a new approach to decrease the infection spreads through banknotes.

Cellulose nanocrystals (CNCs) and cellulose nanofibres (CNFs) were successfully extracted from cellulose obtained from maize stalk residues. A variety of techniques, such as Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA) were used for characterization and the experimental results showed that lignin and hemicellulose were removed to a greater extent by following the chemical methods. Atomic force microscopy (AFM) results confirmed that the diameters of CNCs and CNFs were ranging from 3 to 7 nm and 4 to10 nm, respectively, with their lengths in micro scale. CNCs suspension showed a flow of birefringence, however, the same was not observed in the case of suspension containing CNFs. XRD analysis confirmed that CNCs had high crystallinity index in comparison to cellulose and CNFs. Nanopapers were prepared from CNCs and CNFs by solvent evaporation method. Micropapers were also prepared from cellulose pulp by the same technique. Nanopapers made from CNFs showed less transparency as compared to nanopapers produced from CNCs whereas high transparency as compared to micropaper. Nanopapers produced from CNFs provided superior mechanical properties as compared to both micropaper and nanopapers produced from CNCs. Also, nanopapers produced from CNFs were thermally more stable as compared to nanopapers produced from CNCs but thermally less stable as compared to micropapers.

Two xylose-rich hemicellulose fractions were obtained from kenaf wood (Hibiscus cannabinus L.) through a series of sequential extractions which dissociated xylans from other cell wall components. These fractions were subsequently used as substrates for the production of biologically active aldouronic acids. Incubation of the xylans with a family 10 Thermoascus aurantiacus endoxylanase resulted in the isolation of an aldotetrauronic acid as the main acidic oligosaccharide in the hydrolysis products. Enzymic hydrolysis with a family 11 Sporotrichum thermophile endoxylanase instead resulted in the isolation of a aldopentauronic acid as the main acidic oligosaccharide. The identity and purity of both xylans and aldouronic acids were assessed with solid-state FT-IR, solid-state and solution 13C NMR spectroscopy.

The aim of this study was to develop electrospun chitosan/polyethylene oxide- based randomly oriented fiber mats reinforced with chitin nanocrystals (ChNC) for wound dressing. Microscopy studies showed porous mats of smooth and beadless fibers with diameters between 223-966 nm. The addition of chitin nanocrystals as well as crosslinking had a positive impact on the mechanical properties of the mats, and the crosslinked nanocomposite mats with a tensile strength of 64.9 MPa and modulus of 10.2 GPa were considered the best candidate for wound dressing application. The high surface area of the mats (35 m2.g−1) was also considered beneficial for wound healing. The water vapor transmission rate of the prepared mats was between 1290-1548 g.m−2.day−1, and was in the range for injured skin or wounds. The electrospun fiber mats showed compatibility towards adipose derived stem cells, further confirming their potential use as wound dressing materials.

This paper deals with the effect of solution properties and nanoparticle surface chemistry on the spinnability of a chitosan/polyethylene oxide (PEO) with high concentration (50 wt%) of chitin and cellulose nanocrystals and the properties of the resultant nanocomposite fibers/fiber mats. Electrospinning dispersions with cellulose nanocrystals having sulphate surface groups showed poor spinnability compared to chitin nanocrystals with amide and amino groups. Chitin nanocrystal based dispersions showed good spinnability and continuous fiber formation whereas cellulose nanocrystal system showed discontinuous fibers and branching. The viscosity and surface tension are shown to impact this behavior, but conductivity did not. Poor spinnability observed for cellulose nanocrystal based fibers was attributed to the coagulation of negatively charged cellulose nanocrystals and positively charged chitosan. The study showed that the nanocrystal surface charge and interactions with the chitosan/PEO matrix have a significant impact on the spinnability of bionanocomposites.

This paper addresses the issue of high water retention by cellulose nanofibers (CNFs) that lead to exorbitant time consumption in the dewatering of CNF suspensions. This has been a bottleneck, which is restricting the commercialization of CNF derived products such as nanopapers and CNF reinforced paper sheets. As a remedy, we suggest an eco-friendly water-based approach that involves the use of sonication energy and lactic acid (LA) to modify the surface of CNFs. The suggested modification resulted in rapid water drainage, and dewatering was completed in 10 minutes; with unmodified CNFs, it took around 45 minutes. We have also compared the draining characteristics of LA modification of CNF suspensions with a common draining agent (NaCl); LA modification drains water 56% faster than the use of NaCl, and produced mechanically superior dimensionally stable nanopaper. Additionally, LA modification allows the addition of 10 wt.% CNF in paper sheets, with dewatering done in 2 minutes (while the unmodified CNFs took 23 minutes).

Microcrystalline cellulose (MCC) and cellulose long fiber (CLF) were treated with iron (Fe) based salt and the samples were characterized to study the coordination complexes formed between cellulose and iron. The Fe-modified MCC and CLF were characterized by spectroscopic, thermal and morphological methods. MCC and CLF were oxidized and further treated with iron (Fe) based salt in a high pH medium to form coordination complexes. Both MCC and CLF were then analyzed using Scanning electron microscopy (SEM) to examine their surface morphology. The results have shown that there was no major change in morphology for MCC and CLF upon modification. The functional groups formed by modifying cellulose by iron salt were investigated using FTIR-ATR spectroscopy and the nature of the coordination bonds formed between cellulose and Fe ions were examined by X-ray photo electron spectroscopy (XPS). The results agree that coordination bonds were formed between de-protonated and or oxidized hydroxyl group and Fe ions. Powder XRD (PXRD) was resourceful to compare the crystallinity of unmodified and Fe-modified samples of MCC and CLF. Thermal stability of modified cellulose was studied using thermo gravimetric analysis (TGA). The results showed that there was an increase in percentage of residual mass and higher thermal stability for the Fe-modified MCC and CLF compared to unmodified samples due to the presence of iron.